1. Field of the Invention
The present invention relates to an allocating of a spare area to a recording medium, and more particularly, to a method and apparatus for allocating a spare area to a recording medium for defect management, and a recording medium thereof.
2. Description of the Related Art
Generally, for defect management purposes, a spare area is allocated to a data area of a recording medium. The allocation of the spare area causes the data area to be divided into a user data area and the spare area. The spare area is an area of the recording medium reserved for use when a defect occurs in the data area. When the defect occurs, user data can be recorded in the spare area, thereby enabling a complete recording of user data to a recording medium.
In general, the allocating, in the recording medium, of the spare area is performed during initialization. A ratio of the spare area to the data area is determined based on a defect rate of a recording medium, the characteristics of data to be recorded, the size of the data area, etc.
However, when defects occur more frequently than expected, the spare area may become entirely filled with data, before completing data recording in the user data area. The exhaustion of the spare area prevents defect management from being performed on the remaining portion of the user data area. In contrast, a large part of the spare area may be left to be unused when defects occur less frequently than expected. In the former case, the size of the spare area, associated with the data area, ends up being excessively small, whereas in the latter case, the size of the spare area ends up being excessively large. For both cases, the data area is not efficiently used.
Defect management can be defined as a rewriting of user data, of a portion of a user data area in which a defect is detected, in a new portion of data area of a recording medium, thereby compensating for a loss in data caused by the defect. In general, defect management is performed using linear replacement or slipping replacement. In linear replacement, a user data area, in which a defect occurs, is replaced with a spare data area having no defects. In slipping replacement, user data recorded in a user data area having a defect is slipped to be recorded in the next user data area having no defects.
Both linear replacement and slipping replacement are applicable only to recording media such as a DVD-RAM/RW on which data can be repeatedly recorded and where recording can be performed using a random access method. It is difficult to apply linear replacement and slipping replacement to a write once recording medium, where recording is allowed only once. In general, the presence of defects in a recording medium is detected by recording data on the recording medium and confirming, based on the recorded data, whether or not data can be recorded on the recording medium. However, once data is recorded on a write once recording medium, it is impossible to overwrite new data and manage defects therein.
Meanwhile, after the development of CD-Rs and DVD-Rs, high-density write once recording media have been introduced, with the high-density write once recording media having a recording capacity of several dozens of giga-bytes (GB). These recording media can be used as backup recording media, since they are not expensive and allow random access which enables fast reading operations. However, defect management is not available for write once recording media. Therefore, a backup operation is discontinued when a defective area, i.e., an area where a defect occurs, is detected during the backup operation, because defect management on a write once recording medium is not performed. In general, a backup operation is performed when a system is not frequently used, e.g., at night when a system manager does not operate the system. In this case, it is more likely that a backup operation is stopped when a defective area of a write once recording medium is detected.